1. Field of the Invention
The present invention relates to a vibration driven motor for driving a movable body and a vibrating body relative to each other by a vibration wave, in particular, by a travelling vibration wave.
2. Related Background Art
Conventional vibration driven motors have been proposed in Japanese Patent Application Laid-Open Nos. 1-303072, 2-155480, and the like. In a motor of this type, a ring-like rotor 6 or a stator 3 shown in FIG. 7 is supported by a plurality of support elements radially or obliquely projecting from the rotor or stator main body. The conventional motor will be described in detail below with reference to FIG. 7. FIG. 7 is a longitudinal sectional view showing a conventional vibration driven motor, and FIG. 8 is a perspective view thereof.
In FIGS. 7 and 8, an elastic body 1 and a piezo-electric element 2 are adhered integrally with each other to constitute the stator 3. The rotor 6 is constituted by a rotor ring 4 and a slider 5, and contacts the stator 3 under pressure by a compression member (not shown).
A stator support member 9 has an elasticity, and is provided with a plurality of support elements 9-a, which project radially inwardly from a ring-like main body 9-b, and are arranged at equal angular intervals in the circumferential direction.
FIG. 9 shows the shape of the stator support member. The support elements 9-a are adhered to the lower surface of a flange portion 1-a arranged on the outer peripheral portion of the elastic body 1. The support member 9 is fixed to a fixing member (not shown) by its ring-like main body 9-b.
The rotor 6 is supported by a rotor support member 7 constituted by support elements 7-a integrated with the rotor ring 4, and a rotor support member main body 7-b. The rotor support elements 7-a have an elasticity like in the stator support member 9, and are arranged to extend radially therefrom at equal angular intervals in the circumferential direction.
However, in the conventional vibration driven motor, one end of each stator support element 9-a is integrated with the ring-like main body 9-b fixed to the fixing member (not shown), and the other end thereof is adhered to the flange portion 1-a of the stator 3. For this reason, each stator support element 9-a is restricted in the radial direction. Similarly, one end of each support element 7-(a) of the rotor 6 is integrated with the rotor ring 4, and the other end thereof is supported by the rotor support member 7. Thus, each rotor support element 7-a is also restricted in the radial direction. For this reason, the elastic displacements of the support elements in a direction to bring the rotor 6 and the stator 3 into tight contact with each other cannot be increased either when the support elements project radially, of when the support elements are arranged in an oblique direction. As a result, a pressurizing force between the rotor 6 and the stator 3 can cause a compression nonuniformity as a result of a dimensional precision error or an assembling error in the constituent members, or as a result of pressurizing force changes due to a change in dimensions over time, thus deteriorating motor characteristics.
Furthermore, in a case wherein the support member and other members fixed to the support member have different linear expansion coefficients, or in a case wherein they have the same linear expansion coefficient, when the temperatures of the respective members change or when a temperature gradient is formed among the respective members due to a change in the environmental temperature, a beam deforms as shown in FIG. 10 in a compression state. For this reason, when the support elements 7-a or the support member main body 7-b receives a tension in the longitudinal direction of the beam, a partial force of the pressurizing force of the tension is generated, and the pressurizing force is increased. On the other hand, when the support elements 7-a or the support member main body 7-b receives a compression force in the longitudinal direction, the pressurizing force is decreased. As a result, motor characteristics change inadvertently, and in an extreme case, the adhered portions between the support elements 9-a and stator flange portion 1-a can peel.